Current manufacturing processes for electronic assembly mountings, such as printed circuit board manufacturing processes, produce variations in the flatness of Land Grid Array (“LGA”) sites. These variations occur because of the natural dynamics of the resin flow during the circuit board lamination process. Attempts to control the lamination process to achieve a constant LGA site geometry have not been successful. Flatness variations in LGA sites occur on circuit boards laminated by raw card suppliers and can occur within the same board. These flatness variations resemble either a convex or a concave dish geometry in the LGA site.
Current methods of compensating for such flatness variations utilize a customized LGA insulated backer with varying film thickness for each printed circuit board. Varying film thicknesses are required to compensate for the varying dish shape geometry in the LGA site. The function of the customized insulated backer is to act like a shim that is pushed against the dish shape geometry on the circuit board. This provides uniform loading to the LGA interposer and module.
One drawback with using such a customized insulated backer is that for each circuit board a customized insulated backer is required. This holds true even for different circuit boards of the same model of printed circuit board. Because multiple backers exist for a single printed circuit board model, an assembler can end up using an incorrect backer for an LGA site. An incorrect backer applied to an LGA site can cause reliability problems and failures during use. A reliability failure can occur because of a cracked module due to higher stress from an over compensation of film thickness on the insulated backer, or intermittent opens can occur due to an inadequate load caused by an under compensation of film thickness.